Ioanna Alifieraki e8b8f0c3b0 Revert "ovl: modify ovl_permission() to do checks on two inodes" ... This reverts commit b24be4acd17a8963a29b2a92e1d80b9ddf759c95 which is commit c0ca3d70e8d3cf81e2255a217f7ca402f5ed0862 upstream. Commit b24be4acd17a ("ovl: modify ovl_permission() to do checks on two inodes") (stable kernel id) breaks r/w access in overlayfs when setting ACL to files, in 4.4 stable kernel. There is an available reproducer in [1]. To reproduce the issue : $./make-overlay.sh $./test.sh st_mode is 100644 open failed: -1 cat: /tmp/overlay/animal: Permission denied <---- Breaks access -rw-r--r-- 1 jo jo 0 Oct 11 09:57 /tmp/overlay/animal There are two options to fix this; (a) backport commit ce31513a9114 ("ovl: copyattr after setting POSIX ACL") to 4.4 or (b) revert offending commit b24be4acd17a ("ovl: modify ovl_permission() to do checks on two inodes"). Following option (a) entails high risk of regression since commit ce31513a9114 ("ovl: copyattr after setting POSIX ACL") has many dependencies on other commits that need to be backported too (~18 commits). This patch proceeds with reverting commit b24be4acd17a ("ovl: modify ovl_permission() to do checks on two inodes"). The reverted commit is associated with CVE-2018-16597, however the test-script provided in [3] shows that 4.4 kernel is NOT affected by this cve and therefore it's safe to revert it. The offending commit was introduced upstream in v4.8-rc1. At this point had nothing to do with any CVE. It was related with CVE-2018-16597 as it was the fix for bug [2]. Later on it was backported to stable 4.4. The test-script [3] tests whether 4.4 kernel is affected by CVE-2018-16597. It tests the reproducer found in [2] plus a few more cases. The correct output of the script is failure with "Permission denied" when a normal user tries to overwrite root owned files. For more details please refer to [4]. [1] https://gist.github.com/thomas-holmes/711bcdb28e2b8e6d1c39c1d99d292af7 [2] https://bugzilla.suse.com/show_bug.cgi?id=1106512#c0 [3] https://launchpadlibrarian.net/459694705/test_overlay_permission.sh [4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1851243 Signed-off-by: Ioanna Alifieraki <ioanna-maria.alifieraki@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-04-07 13:49:58 +02:00
..
copy_up.c
dir.c	ovl: fix uid/gid when creating over whiteout	2020-04-06 15:28:07 +02:00
inode.c	Revert "ovl: modify ovl_permission() to do checks on two inodes"	2020-04-07 13:49:58 +02:00
Kconfig
Makefile
overlayfs.h
readdir.c
super.c